I tend to feel kind of negative toward it, mostly because I like boobs and because I've seen the scars that reductions can leave. Christina Ricci is a pretty famous example, but I also know someone personally who had to have them reduced because it was making an existing problem with her back even worse. Yeah, it's not my body, so I can't really say much, other than that it makes me feel a bit sad. Probably the saddest example I know of is when one of the Suicide Girls I liked quite a bit who had a very nice figure said she was going to get breast reduction surgery basically because she felt like they were gaining her too much negative attention - like people would be staring at her and in particular other women would be giving her the stink eye and making comments amongst themselves about her supposedly having implants. I think it's horrible that she would go under the knife because people are being assholes to her. I don't know if she went through it or not, but she hasn't had any new sets since she talked about doing it back around 2009 or so. Doing it for medical reasons is definitely understandable, and the sadness there comes from the necessity.
The only one I'd really try to talk out of it would be one like that Suicide Girl I mentioned. I'm going to assume anyone talking about doing it isn't just doing it on a lark or something like that, so I wouldn't say anything otherwise.